Method and device for measuring the condition of steel structures

Abstract

Method and apparatus for measuring parameters in ferromagnetic steel structures, e.g. railway rails and drill pipes, to detect mechanical stress, damage and deterioration. On the monitored structure, devices for magnetization or demagnetization e.g. an electromagnet, will be installed. Two or more electrodes for feeding of a pulse shaped electrical voltage are installed. Across another pair of electrodes, a voltage response signal is measured, and compared with another response signal measured under known conditions or compared with calibration data for the structure. The deviation between these voltages is analyzed to quantify the relative or absolute deviations, and the condition of the steel structure is estimated. The device can measure the transient voltage curves with reference to one or more of the magnetization curves and includes algorithms for analyzing the voltage response curve for determination of mechanical stress and / or fatigue and / or cracks and / or metal loss in steel materials.

Description

BACKGROUND OF THE INVENTIONThe present invention is directed to a method for measuring the condition of a steel structure. Furthermore, it comprises a device for carrying out such measurements of condition of a steel structure. The method can be adapted for detection of mechanical stress, fatigue and metal loss e.g caused by corrosion.More particularly the invention concerns a method for measuring the condition of a steel structure, whereby a pulse-shaped electrical current is applied to the steel through a pair of contact points, generating potential drop curves between another pair of contact points measured by repeated sampling. The steel subjected to the measurements can both be magnetized and demagnetized by means of arrangements known per se and being employed for magnetization of the steel to selected points at the initial, the anhysteretic and hysteretic magnetization curves. Comparison of the potential drop curves at different magnetization makes it possible to determine th...

AI Technical Summary

Benefits of technology

"The invention provides a method for monitoring different types of structures, such as metal pipes, for defects that can cause deterioration and damage. The method can detect changes in steel caused by excessive loads, fatigue, and cracks with high sensitivity and accuracy. The method can also measure the degree of deterioration caused by metal loss and corrosion. By measuring the transient voltage drop when monitoring metal loss, the method can determine the wall thickness of the pipe. The method can be used in sensors and can be incorporated into existing monitoring systems."

Problems solved by technology

Large steel structures are often subjected to varying loads causing deterioration.

Mechanical stress can arise unintentionally both during construction, (for example in or adjacent to weld seams) and during operation because of uncontrollable conditions.

By using of such methods changes are measured from the instant the arrangement is installed with respect to absolute mechanical stresses the possibilities are more limited.

Thus, according to the patent a prejudice exists against the consideration of the transient portion of the voltage drop curve to provide information on possible defects or changes in the structure.

The disadvantage is that for large pipes with large wall thickness the transient time is long and for practical applications and for other reasons measurements are made before the transient has decayed.

However, this patent does not describe how the method responds to fatigue.

Furthermore, these measurements do not consider the information inherent in the stationary part of the voltage response, which includes significant information about the fatigue.

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